Polycyclic Aromatic Hydrocarbons (PAHs) were determined in sediments and bivalves by the Gas chromatography coupled to Mass spectrometer (GC/MS). PAHs concentrations in sediments of My Bousselham and Khnifiss, Atlantics lagoons, (expressed as ∑PAH) ranged from 31 to 82 ng/g of dry weight and from 6.6 to 34 ng/g of dry weight, respectively. Concerning organisms, PAHs levels contamination ranged from 28 to 117 ng/g of dry weight for My Bousselham (Ruditapes Decussates) and from 7 to 18.5 ng/g of

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... ry weight for Khnifiss Lagoon Oyster (Crassostrea gigas). In the Med Lag (Nador), the results obtained showed a range varying from 6 to 126 ng/g of dry weight for sediments and from 24 to 32 ng/g of dry weight for organisms (Mytilus Galoprovincialis). The origin investigation of PAHs in sediment revealed, that the process of combustion was the main source in these Lagoons, while the diagenetic source, related to the high concentrations obtained of Perylene, was established only in both Atlantics Lagoons (Khnifiss and My Bousselham). A prevalence of high molecular weight PAHs was observed, with a considerable predominance of 4-ring PAHs in sediments and organisms of the My bousselham and Nador lagoons, while, no clear predominance was observed in the compartments studied in the Khnifiss lagoon. Correlation study of individual PAH between sediments and organisms, showed that absorption by Clams of low molecular weight PAH group, of which correlation was low, could be done through the water dissolved form, while the absorption of heavier molecular weight PAHs, which showed a high correlation of their distribution between sediments and Clams, could be the absorption from particulate matter.